It actually does cover this on the website but you do have to put the 2 and 2 together
First, at the top, it states
Each lightsaber builder may have one guest, but please do not include the guest in the number of participants—only include the number of actual builders.
Then when you go to look for a reservation is has
Select the Number of Participants
Please see the
Terms and Conditions for information about age requirements. When making your selection, do not include Guests who will be accompanying the participants.
Click on "Terms and Conditions" and is shows
Age recommendation to participate in this program is 5 years and older"
The age requirements is related to Participants, not guests. And it's a recommendation, not requirement. So different than say, BBB, which is required 3-11
Does that mean every CM working will grasp the connection? Does that mean that every single parent should bring their too young child?
No
But I in no way agree that Disney will refuse a single parent the ability to participate in the activity (aka take their money). It's going to be up to the parent to know if it's a valid activity for their child to accompany them on.